Conversion process



May l, 1945.

H. C. MAYLAND CONVERSION PRocEss Patented May 1,-1945 y UNITED STATES VPATEIW oFFicE CONVERSION PRocEss Harrison C. Mayland, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application March 26,1942, Serial No. 436,305

6 Claims.

This invention relates to a'process for the conversion of organic materials and, more specifically, to the conversion of hydrocarbons.

'I'he present invention is particularly applicable to the dehydrogenation of hydrocarbons. In view of the extreme importance at the present time, of the production of styrene for use in connec patents. Ethylbenzene may also be produced by.

dehydrocyclization of'octanes or octylenes and is also produced in the catalytic reformingof gasoline or naphtha, and particularly when the reforming process is conducted in the presence of.

hydrogen in the type of process now known in the art as hydroforming. It is also produced in varying quantities during thecracking, and preferablythe catalytic cracking, of higher boiling oilstoproduce gasoline.

'I'he present invention includes 'a number of important features which are essential to a coin- (Cl. 26o-669) hydrogenatlon-catalyst under dehydrogenating conditions, separating the products of said dehydrogenation by flashing in two or more stages, employing substantially the same temperature and increasing pressures,'nally separating theI products of said conversion, and recycling the unconverted benzene to the process for 'further conversion therein. The accompanying diagrammatic drawing illustrates several specilicmethods in which the present invention may beV conducted `but not with the intention of unduly limiting the Same.

Referring to the drawing, ethyibenzene is m-- troduced to the process through line l to pump 2,

mercial process for the production of styrenefrox'n ethylbenzene. These various features will be described in detail in the following specification and claims.

One important feature of the present invention resides in the method of preliminarily separating the conversion products from the catalytic reactors. This step of the process comprises atwo or three-stage hashing system which will hereinafter be described in detail.

. Another feature of the preselt/inention, as applied to the catalytic dehydrolzenationl of ethylbenzene, is the recycle of the unconverted ethylbenzene from the final separationzone back to' the process for further conversion therein. Another feature is theuse of relativelylow pressures,

by means of whichlit is directed through line 3 and pump 4 toprocess heater 5. 'lhe process heater may comprise any suitable apparatus, by means of which the ethylbenzene is heated to the desired temperature which may range from about 1000 F. to about 1200L7 F. 'Ihe products from heater 5 are directed through line 6 into catalytic reactors 'I and 8.

Although illustrated in the drawing as comprising tworeactors, it is understood that the` process may employ one or three or more catalytic reactors. Usually the reactors are employed in multiples of two so that one or any number thereof may be undergoing processing while the catalyst in the other one or any number thereof may be undergoing regeneration.

The particular catalyst employed in the process will depend upon the reactionl desired. For

example, in the dehydrogenation of ethylbenzene to styrene, any satisfactory dehydrogenation catalyst may be employed. A suitable catalyst includesalumina, magnesia, or other suitable Arefractory oxides composited with a compound,

' and preferably an oxide, of the elements in the preferably subatmospheric in the catalytic dehydrogenatlon reaction. These .and other features of the invention will be hereinafter more In one specific embodiment, the present inven- -tion relates to a process for-.the dehydrogenation of ethylbenzene to styrene which comprisessub- 'jecting said ethylbenzenev tocontact with Va `deleft-hand columns 0f groups IV, V, and VI of the periodic table. One of the preferred catalysts comprises alumina composited with chromia.v It is understood thatI these or other catalysts will not entirely be equivalent in their activity and that the conditions of operation will be modified Assuming that catalyticreactor 'l is being' used for processing, the. heated ethylbenzene will be directed through linie 9, valvelll, line Il and line I2 into catalytic reactor l. 'Iheheated products are introduced into the reactorat a relatively low pressure, whichV pressure mayV range, for example, from 1%; pounds absolute up to 20 pounds' 'v absolute. 'Usually a subatmosphenc'pressure of abouti pounds absolute is preferredxLiquid hourly space velocities employed range from y0.5

suitable method includes the use of substantially4 adiabatic operations, in which case either the charging stock is heated to a sufficiently high 1 temperature or a heated extraneous material is introduced with the charging stock to supply the heat of reaction. Another suitable method is illustrated in the drawing, which comprises passing a heat convective medium in indirect heat exchange with the products undergoing conversion. vInthis type of operation a tubular heat exchanger type reactor may be employed and preferably is designed for a-low pressure drop. The catalyst is usually disposed within the tubes and a suitable convective medium isl passed through the space surrounding the tubes. Another suitable type of reactor is of the form illustrated and described in United States Patent No. 2,252,719. The heat convective medium may comprise either normally gaseous, liquid or solid material. One suitable material includes a molten salt, which salt is circulated in large quantities through the space surrounding the catalyst sections. Referring to the drawing, the heat convective medium is introduced to reactor 1 through line I3 and removed therefrom through line I4. v

The conversion products from reactor 1 are withdrawn therefrom through line I4' and passed through steam generator I5, line I6, process cooler I1, into line I8. It is understood, of

course, that any other suitable means of cooling the hot conversion products to the desired temperature may be utilized. One convenient means includes passing the fresh and/or recycled. ethylbenzene in indirect heat exchange with the products from reactor 1, either by the use of cooler I1 or by any other suitable type of exchanger. It is also within the scope of the invention to omit steam generator I5 when desired.

While reactor 1 is being utilized for electing the dehydrogenation reaction, the catalyst in reactor 8 is being regenerated. Regeneration is accomplished by burning the carbonaceous material from the catalyst with nue gases containing the required amount of oi'rygen.v This system usually comprises purging the reactors with4 oxygen free gases before and after the burning operation. The regeneration gases are supplied through line I9, line 20, valve 2|, line 22 .and line 23 into contact with the catalyst and the regeneration gases therefrom are passed through line 24, steam generator 25, line 26,- process cooler 21 into `line 26. Likewise, steam-generatory 25l and process cooler 21 may be modied in the same manner as heretofore described in connection with steam generator I6 and process cooler I1 Manifold line 29,.valve 30, line 3|; aswell as line 32, valve 33 and line 34, are utilized when it is desired to switch the processing and catalyst regeneration cycles between reactors 1 and 8.

While the catalyst in reactor 8 is undergoing regeneration, heat 'is liberated .due tothe exothermicity of the reaction, and it will be necesy sary to cool the same in order to avoid excessive temperatures which may prove detrimental to the catalyst. The cooling of reactor 8 may be accomplished in a similar manner as thatdescribed preliminary separation system. Theyregenerating gases from reactor 8 are passed through line 28, line 42, valve 43, line 44, and line 45' to a suitable recovery system. When reactors '1 and 8 are switched as regards the processing and catalyst regeneration, regenerating gases would be supplied to reactor 1 in the manner heretofore described and would be removed through lines I4', I6 and I8, and then directed through line 45, valve 46, line 41, into and through line 45'. `At the same time, the dehydrogenation conversion products would be passed through lines 24, 26 and 28 through line 48, valve 49, line 50, into and. through lines 40' and 4I.

The products passing through line 4I contain unconverted ethylbenzene, styrene, some toluene and benzene, a higher boiling residue, and light gases. An important feature-of the pres'ent invention is the method to be presently described for the preliminary separation of these products. Both styrene and ethylbenzene are relatively expensive products and their recovery to the greatest extent is of importance. This is accomplished according to the features of the present invention. v v

The conversion products in line 4I are preferably cooled by the means heretofore described to a temperature within-the range of 50 F. to 200 F. andv usually about 100 F. Reactors 1 and 8, steam generators' I5 and 25, process coolers I1 and 21, pipe lines and switch valves are preferably designed so as not to effect too great a pressure drop in order that the conversion products may be introduced to the rst flash drum at substantially the same or only la slightly modiiicd pressure to that utilized in the catalytic reactors.

The conversion products are passed through line 4I into flash drum 5I. In hash drum 5I a rough separationbf the products introduced drum 5I through line 52 to pump 53, by means of which they are directed through line 54 into separation zone 55.

-The non-condensed products from zone 5I are withdrawn through line 55' and directed to compressor 56, by means of which they are raised to a pressure of between about atmospheric and about 50 pounds superatmospheric and directed through line 51 and cooler 58. n cooler 58 the products are cooled to the desired temperature, which may range from about'50.F. to -about 200 F., and the cooled products are then directed through line 59'into flash drum 60. In flash drum 60 an additionalseparation of the conversion products is effected. The condensed products are withdrawn therefrom 'through line 6I to pump. 62, by means of which they une' es 1pm une sa'.

m @ne embodiment or the mention,v particu;

are directed throughv from zone I contain substantially no, or relatively minor proportions of, ethylbenzene or sty-A rene, the non-condensed vapors may be withdrawn from zone 50 through line 64 and discharged from the system. However, in another embodiment of the invention,- particularly when this portion contains a suflicient quantity of ethylbenzene and styrene to economically justify their further recovery, the non-condensed products withdrawn from zone 50 may be directed through asI the absorption oil heretofore mentioned, it is within the scope of the invention to direct all or a portion of the separated benzenek and/ or toluene through line 11 to pump 1l, by means of which it may be directed through line 19, Il, 51,

' and 59. to flash drum 10 for use therein as hereline 65 to compressor 66, by means of which they are raised to a pressure of between about 50 and about 200 pounds or more, and then directed through line 51 to cooler 58.. 'I'he products in passing through cooler 58 are cooled to the desired temperature, which may range from between about 50F. and about 200 F., and are then paed through line G9 into flash drum 10.

The products introduced into flash drum 10 will comprise a large proportion of normally gaseous material anda minor proportion of normally liquid material. This has the tendency of dissolving some of the normally gaseous, material in the normally liquid material and, as a particular feature of the present invention, an absorption oil is commingled with the compressed products in line 51. Alternatively, the absorption -oil may be commingled with the compressed produucts after cooler 58, if desired. The absorption g oil in this step of the process serves to absorb the remaining minor quantities of ethylbenzene and styrene and at the same time absorbs some of the lighter gases. Any suitable absorption oilV may be` usedjn this step of the process, the major requirement being that the absorption oil will not vaporize and be withdrawn with the gaseous products'under the conditions of operation maintained in zone 10. The unabsorbed and uncondensed lighter productsare withdrawn from zone tofore described.

Unconverted ethylbenzene is withdrawn from zone 55'through line 8l and all or a portion is withdrawn from the process. Preferably, however, at least' a portion of the ethylbenzene is recycled by way of line 8|', pump 82, line 83, and line 3 to heater 5 and reactors 1 and 8. A higher boiling residue is withdrawn from zone 55 through line 85 and may be removed from the process. Since this material also appears satisfactory'for use as the absorption oil, at least a portion thereof may be directed through line 86 to pump I1, by means of lwhich it maybe directed through lines 88, 89, and 80 to flash drum 10. In case itis desired to use all or a portion of the absorption oil from an extraneous source, the absorption oil may be introduced to the process by Way of line 90, pump 9L into lines 89 and 80, to flash drum .10.

In'another embodiment of the invention, par ticularly when an absorption oil is not utilized, the liquid products from ash drum 10 may be directed through lines 14, branch line 92, and line 54, into separation zone 55.

The following examples are introduced for the purpose of further illustrating the invention and 10 through line 12 to pump 13, by means of which v oi and withdrawn through line while the liquid products are withdrawn through line 52 and directed into the final separation step of the process. l

Zone 5,5 may comprise any suitable type of process to effect the desired separation between the styrene and other products introduced thereto. Since no novelty is claimed herein for the separation step as such, there appears no need for a detailed recitation thereof in the present application. Whichever process is usedin zone 55, the products introduced therto are separated into normally gaseous products, benzene and'toluene, either together or separately,` unconverted ethylbenzene,.styrene. and a higher boiling residue. .The normally gaseous products will comprise a very minor per cent of the products introduced into zone 55and this greatly facilitates the subsequent separation and recovery of styrene and ethylbenzene. This is one ofthe important advantages ofthe dashing system heretofore de. scribed. The normally gaseous products are removed from zone 55 through line 15 to storage or elsewhere, as desired. Benzene and toluene may be separately recovered or recovered in adinixmreandwithdrawniromtheprocessthrough' line 15toorelsewhere,asdesired. Since A and/or toluene'are satisfactory for use sorbed gases are separated in this zone, while the which an absorption oil is not utilized, the procnot with the intention of unduly the` troduced to ash drum 5I at a temperature of about F. and a pressure of about 5 pounds absolute. The liquid and non-condensed products are separated, the liquid products being. directed to separation zone 55, while the non condensed products are compressed to a preure of about 25 pounds absolute or 10 pound gauge, cooled to a temperature of about 100 F. and introduced into ilash drum 51|. The liquid products are separated from the non-condensed products, thel liquid products being directed into separation zone 55, while themen-condensed products are compressed to a pressureof about pounds absolute, commingled with an absorption oil, cooled to a temperature of about 100 F. and introduced into flash drum 10. 'I'he procs gas is withdrawn from the upper portion of zone 1l and contains substantially no, or perhaps onlyminute quantities of, ethylbenzene or styrene.

The liquid products withdrawn from ash drum 10 are returned to flash drum 5I and any abnormally liquid products, including the ethylbenzene and` styrene, are withdrawn from the lower portion of this zone and are supplied to nal separation zone 55.

In the other embodiment of the invention, in

ess is conducted substantially as set forth inthe .paragraph withthe exception that the liquid products from ilash drum 1I are commingledwith the liquid products withdrawn from ash drums 5I and 60 and the commingled liquid products are directed to separation zone 55.v In this embodiment of the invention minor quantitles of ethylbenzene and styrene are withdrawn with the process gases from the upper portion of iiash drum 10. This embodiment of the invention may be preferred when difculty is encountered in zone 55 in the final separation of styrene' from the other products. The particular dashing system to be employed will ythus depend in part upon the particular final styrene separation process employed.

I claim as my invention:

1. A process for separating the conversion products formed in the dehydrogenation of ethylbenzene under subatmospheric pressure which comprises cooling the products of -said dehydrogenation; introducing the cooled products into a rst separation zone at substantially the same pressure as employed in said dehydrogenation, separating condensed from uncondensed materials in said first separation zone, withdrawing the uncondensed materials from said iirst separation zone and compressing the same to a higher pressure and introducing the compressed materials into a second separation zone, separating condensed from uncondensed materials in said second separation zone, withdrawing the latter from said second separation zone and compressing the same to "a higher pressure, commingling an absorption oil with the compressed materials from said second zone and introducing the same to a third -separation zone, separating uncondensed and unabsorbed materials from the condensed and absorbed materials in said third separation zone, withdrawing the former from the .process. and introducing the condensed and abjsorbed materials into said rst separation zone, withdrawing the liquid products from said first separation zone and'commingling the same with the condensed second separation zone, and separating styrene and unconverted ethylbenzene from the commin gled materials.

2. A process such as defined inv claim 1, wherein said absorption oil comprises benzene which is recovered during the separation of the said unconverted ethylbenzene and styrene.

' 3. A process such as dened in claim 1, wherein said absorption oil comprises toluene which islre'- covered during the separation of the said unconverted ethylbenzene and styrene.

4. A process such as dened in claim 1, wherein said absorption oil comprises benzene and toluene which are recovered during the separation of the said unconverted ethylbenzene and styrene.

- 5. A process such as defined in claim 1, wherein said absorption oil comprises material boiling higher than styrene, which higherA boiling, material is recovered during the separation of said ethylbenzene and styrene from the other products of the process.

6. A process for separating the conversion products formed in the dehydrogenation of ethylbenzene to styrene, which comprises cooling said products and separating condensed from uncondensed materials in a first zone, compressing the uncondensed materials and separating resultant liquid from the remaining gaseous products in a second zone, commingling an absorption oil with the gaseous products from said second zone to absorb components of the latter in the former, introducing the' thus enriched absorption oil to said iirst zone to remove absorbed light gases therefrom, supplying the liquid materials'from said iirst and second zones to an additional separating zone and therein separating styrene, un'- converted ethylbenzene and absorption oil from the commingled materials. v

' N C. MAYLAND.

materials withdrawn from said- 

